1. Field of the Invention
The present invention relates in general to a system and method for retrieving moving picture data, and more particularly to an apparatus and method for retrieving a moving picture using a descriptor of a tree-structured moving picture index, in which the tree-structured moving picture index is created on the basis of the contents of moving picture data, defined Was the descriptor and then applied to a retrieval system, so that the moving picture data can readily be retrieved.
2. Description of the Prior Art
In a conventional picture data retrieval system, there have been employed a technique for grouping and browsing pictures in a still picture database to provide a structured access to the user, a technique for retrieving a still picture using a tree-structured vector quantizer, and a technique for grouping shots to browse moving pictures.
However, the above techniques are adapted to take still pictures as objects to be retrieved, or lead a user""s search to repetitive browsing rather than query-based automatic retrieval. For this reason, such techniques are not suitable to application environments where moving picture frames are automatically retrieved on the basis of a query.
Further, in extending the above techniques, it is inevitable to use an unnecessary or complex data structure in process of describing or storing data, and the application range is also limited. For example, in the case where the still picture retrieval technique based on the tree-structured vector quantizer is extended and applied to moving pictures, picture groups and a median in each group should be stored as additional data, and the number of objects exhibits an exponential increase with an increase in tree size.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus and method for retrieving a moving picture using a tree-structured moving picture index descriptor, thereby enhancing a moving picture retrieval efficiency.
In accordance with one aspect of the present invention, in a system for retrieving a moving picture in response to a query from the user, there is provided an apparatus for retrieving the moving picture using a descriptor of a tree-structured moving picture index, comprising a decoder for storing the tree-structured index descriptor and feature vectors and outputting object information of the index descriptor and any one of the stored feature vectors designated by a specific key frame number in response to an external request; a query processor for receiving various user-defined values and a query picture/picture sequence from the user in response to the query from the user, extracting a feature vector and retrieval precision desired by the user from the received user-defined values and query picture/picture sequence and generating a retrieval request signal; a stack being a storage medium; a stack controller for sending a retrieval request signal to the decoder in response to the retrieval request signal from the query processor, receiving an in-index highest-order key frame number from the decoder, stacking the received highest-order key frame number in the stack, receiving in-index edge information from the decoder, stacking a key frame number based on the received in-index edge information in the stack, reading the stacked key frame number from the stack and outputting it as the specific key frame number to the decoder; a first syntax analyzer for receiving the in-index highest order key frame number and in-index edge information from the decoder, transferring them, to the stack controller, receiving a list of frame representative threshold values from the decoder and transferring the received threshold value list externally; a feature vector comparator for comparing the feature vector designated by the specific key frame number from the decoder with the feature vector extracted by the query processor and outputting the compared result externally; a threshold comparator for comparing the compared result from the feature vector comparator with the retrieval precision extracted by the query processor and the frame representative threshold value list transferred by the first syntax analyzer to determine whether the specific key frame number from the stack controller is concerned with the query picture and generating a control signal in accordance with the determined result; and an accumulator for accumulating the specific key frame number from the stack controller in response to the control signal from the threshold comparator and outputting the accumulated result finally if the stack is empty.
In accordance with another aspect of the present invention, there is provided a method for retrieving a moving picture using a descriptor of a tree-structured moving picture index in response to a query from the user, comprising the steps of a), if the user starts the query, allowing a query processor to receive user-defined values and a query picture/picture sequence from the user, extract a feature vector and retrieval precision desired by the user from the received user-defined values and query picture/picture sequence, output the extracted feature vector and retrieval precision respectively to a feature vector comparator and a threshold comparator and send a retrieval request signal to a stack controller; b) allowing the stack controller to send a retrieval request signal to a decoder upon receiving the retrieval request signal from the query processor; c) allowing the decoder to output a key frame number of an in-index highest-order node, included in an index object, and in-index edge information and a list of frame representative threshold values, included in a key frame object, to a syntax analyzer in response to the retrieval request signal from the stack controller; d) allowing the syntax analyzer to transfer the key frame number of the in-index highest-order node and the in-index edge information from the decoder to the stack controller and the frame representative threshold value list from the decoder to the threshold comparator; e) allowing the stack controller to stack the key frame number of the in-index highest-order node and the in-index edge information from the syntax analyzer in a stack; f) allowing the stack controller to read a specific key frame number from the stack and transfer it to the decoder and an accumulator; g) allowing the decoder to output a feature vector designated by the specific key frame number from the stack controller to a feature vector comparator and then allowing the feature vector comparator to compare the feature vector from the decoder with the feature vector extracted by the query processor at the step a) and output the compared result to the threshold comparator; h) allowing the threshold comparator to compare the compared result of the two feature vectors from the feature vector comparator with the retrieval precision extracted by the query processor at the step a) and the frame representatives threshold value list transferred by the syntax analyzer at the step d) to determine whether the specific key frame number from the stack controller is concerned with the query picture; i) returning to the step f) if the specific key frame number from the stack controller is not concerned with the query picture at the step h) and accumulating the specific key frame number from the stack controller in the accumulator if the specific key frame number is concerned with the query picture at the step h); and j) determining whether the stack is empty and allowing the accumulator to output the accumulated result to the user if the stack is empty.
In accordance with yet another aspect of the present invention, there is provided a method for retrieving a moving picture using a descriptor of a tree-structured moving picture index, comprising the steps of a) creating the tree-structured moving picture index, the step a) including the steps of a-1) upwardly sampling, an original moving picture partitioned into shots, defining each sample as a node and implying a quantitative representative relation between a sample layer and a mother layer in each edge, and a-2) repeating the step a-1) to accumulate samples into a tree structure; b) describing the created tree-structured moving picture index, the step b) including the steps of b-1) expressing key frame information and shot information respectively as randomly accessible individual objects and then expressing subordinate and representative relations between the objects using attributes, b-2) reflecting information about a highest-order node in the index and the entire information of moving picture data in a third object, and b-3) appending annotation to each of the objects using a descriptor created by the steps b-1) and b-2); and c) retrieving the moving picture using the described tree-structured moving picture index, the step c) including the step of retrieving the moving picture in connection with a retrieval precision desired by the user on the basis of the fact that each frame in the index is representative of a sub-tree, which has it as a vertex, within the range of a quantitative threshold value.